Morgan A, Ampomah W, Grigg R, Czarnota R, Wang S
Petroleum Recovery and Research Center, New Mexico Tech, Socorro, NM, USA.
Department of Petroleum and Natural Gas, University of Energy and Natural Resources, Sunyani, Ghana.
Sci Rep. 2025 Jul 26;15(1):27255. doi: 10.1038/s41598-025-11379-y.
An indispensable factor in developing improved enhanced oil recovery (EOR) is the in-depth insight into the fractional flow mechanistic effects of waterflood performance, especially for an inefficient waterflood operated field. In this study, the inefficiency of waterflood on the Farnsworth Field Unit (FWU) is investigated. The field is divided into two halves (East and West) of the same reservoir with similar geological characteristics. Though the east was prolific on primary recovery, it failed on waterflood, while the west performed efficiently. Through core-flood experiments, fluid-fluid surface charge tests, and rock-fluid surface chemistry analysis, the causative mechanisms are unraveled. X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) analyses were also conducted to assess mineral composition, pore characteristics and distribution. The core samples exhibited extremely low permeability, resulting in a drastic reduction in flow capacity. Single-phase injection of low salinity water (SIIW) further reduced permeability and increased differential pressure compared to high salinity water (SCW). pH and effluent ionic compositions showed a high reactivity within the rock samples. Fine migrations, clay swelling, scaling, and precipitation were identified as key causes of formation damage during low salinity water flooding. Surface charge and compatibility tests revealed fluid-fluid and rock-fluid reactivity and scale formation influenced by high ionic concentrations, temperature, and pressure. Geochemical analysis indicated aragonite, calcite, and dolomite precipitation under reservoir conditions. Element-mineral identification analysis revealed clays and mineral particles obstructing pores and pore throats. Thus, the principal mechanisms of waterflood inefficiency include low permeability, clay mineral reactivity and fluid incompatibility. These factors collectively contribute to formation damage pore and reduced flow capacity. These insights contribute to the development of effective and improved recovery strategies for incremental recovery from the FWU-east field and addition of new knowledge to existing information on low salinity waterflooding on a Morrowan sandstone.
开发改进的强化采油（EOR）技术的一个不可或缺的因素是深入了解注水性能的分流机理效应，特别是对于注水效果不佳的油田。在本研究中，对法恩斯沃思油田单元（FWU）注水效率低下的情况进行了调查。该油田被划分为具有相似地质特征的同一油藏的两个区域（东部和西部）。尽管东部在一次采油阶段产量颇丰，但注水效果不佳，而西部则注水效果良好。通过岩心驱替实验、流体-流体表面电荷测试和岩石-流体表面化学分析，揭示了其成因机制。还进行了X射线衍射（XRD）、扫描电子显微镜和能量色散X射线光谱（SEM/EDS）分析，以评估矿物成分、孔隙特征和分布。岩心样品渗透率极低，导致流动能力急剧下降。与高盐度水（SCW）相比，单相注入低盐度水（SIIW）进一步降低了渗透率并增加了压差。pH值和流出物离子组成表明岩石样品内部具有高反应性。细颗粒运移、粘土膨胀、结垢和沉淀被确定为低盐度水驱油过程中地层损害的关键原因。表面电荷和配伍性测试揭示了流体-流体和岩石-流体的反应性以及高离子浓度、温度和压力对结垢形成的影响。地球化学分析表明在油藏条件下有文石、方解石和白云石沉淀。元素-矿物鉴定分析表明粘土和矿物颗粒堵塞了孔隙和喉道。因此，注水效率低下的主要机制包括低渗透率、粘土矿物反应性和流体不相容性。这些因素共同导致地层损害孔隙并降低流动能力。这些见解有助于制定有效的改进采油策略，以增加FWU东部油田的采收率，并为现有的关于莫罗砂岩低盐度注水的信息增添新知识。
